Chill tubes are known to have rectangular inner and outer cross sections, as well as having rounded longitudinal edge regions which have a nominal wall thickness that is 8% to 10% of the distance between the inner surfaces lying frontally opposite to each other at the tube opening.
Moreover, it is known for chill tubes that one may put the inner surfaces indirectly under the influence of cooling media that remove heat and are able to be supplied to the tube wall from the outside. In this connection, the chill tubes may be furnished on their outer contours with fitted jackets, which form exactly specified gaps together with the outer surfaces of the chill tubes, through which cooling media may be conducted. The cooling media may also flow through cooling channels put vertically into the walls of the chill tubes. Finally, it is also known that one may apply cooling media to the outer surfaces of the chill tubes via spray nozzles.
In the course of practical efforts to increase casting speeds, namely to rates greater than 2.5 m/min, the then-existing heat may only still be transferred partially to the cooling media removing the heat, on account of the limited heat transfer capacity of the basic materials of the chill tube. The result is partial overheating and, in this context, damage to the inner surfaces of the chill tubes. This circumstance may be observed especially in the high ranges of the bath levels which vary in their level, and in the region of the first phases of primary solidification of the metals to be cast, because in those locations there prevails the greatest heat supply to the chill material.